*Always insist that you see the repair shop's "F" gas certificate.*
This is the very basic requirement for anyone handling your car a/c.
                Did you know that: Car Air Conditioning does not provide "COLD" air!!
A/C Compressor Operation 
Below is an overview of an A/C compressor and its operation 
The Compressor 
The compressor used to air condition your car works in a similar way to the one in the refrigerator in your
kitchen. The job of the compressor is to move liquid 
refrigerant around in a pipe. The compressor pumps, or forces, the liquid from the 
evaporator into a condenser and expansion valve, and then back to the evaporator. 
There are three common types of compressors: 
Two cylinder reciprocating piston type 
Four cylinder RADIAL type 
Six cylinder AXIAL type 
The engine drives the compressor with a belt. In action, the compressor takes the 
low pressure refrigerant from the evaporator and compresses it according to speed 
and air temperature. The inlet side is known as the low (pressure) side and the 
outlet side is known as the high (pressure) side. 
The compressor compresses the refrigerant, and raises its temperature higher than 
that of the surrounding air. Then, the compressor forces the refrigerant into the 
Compressor Clutch 
The air conditioning compressor has an electromagnetic clutch that can engage or 
disengage the compressor pulley. The compressor pulley always turns when the engine is running, but the compressor only runs when the pulley is engaged to the 
compressor driving shaft. 
When this system is activated, current runs through the electromagnetic coil. The 
current attracts it to the armature plate. The strong magnetic pull draws the 
armature plate against the side of the turning pulley. This locks the pulley and the 
armature plate together; the armature plate drives the compressor. 
When the system is deactivated, and current stops running through the 
electromagnetic coil, flat springs pull the armature plate away from the pulley. 
The magnetic coil does not turn since its magnetism is transmitted through the 
pulley to the armature. The armature plate and hub assembly are fastened to the 
compressor drive shaft. When it's not driving the compressor, the clutch pulley turns 
on a double row of ball bearings. 
AC Compressor Drive Ring 
Inside the air conditioner's refrigerant compressor is a drive ring made of a friction 
material that is mounted to both sides of the "swash" or "wobble" plate. As the 
swash plate rotates, the friction material pushes the ball bearings (mounted to the 
pistons) back and forth. 
The Condenser 
The condenser is a long tube that goes back and forth through a multitude of cooling 
fins, quite similar to the evaporator in structure. The condenser is mounted in front 
of the radiator to take advantage of the forced air provided by the fan and the 
motion of the car. 
As the highly pressurized refrigerant (vapor) flows into the condenser, it gives off 
heat and warms the condenser. This causes the condenser to be hotter than the 
forced air coming through the condenser. The condenser hands its heat off to the 
forced air and turns the refrigerant back into cool liquid in the expansion valve, 
where it heads back to the evaporator. 
The Evaporator 
The evaporator is a long tube, or coil, that goes back and forth through a multitude 
of cooling fins. It is quite similar to the condenser in structure. 
The refrigerant is a liquid when it enters the evaporator. A fan blows warm air over 
the evaporator. The warm air causes the liquid refrigerant to boil. This means that it 
absorbs the heat from the warm air. Once it has absorbed the heat from the warm 
air, the warm air isn't warm anymore. The same blower that blows the warm air 
(that is now "cool" air) over the evaporator, keeps on blowing it into the interior of 
your car, and you have -- air conditioning! 
The evaporator also removes the moisture from the air coming through its fins and 
turns it inthe to water. The water just drains off. The temperature of the evaporator coil can go from 33 degrees F to 0 degrees F. If it 
goes below 32 degrees F, the moisture that's supposed to drain off the coils will 
freeze. This makes for a very (surprise!) inefficient system, so a thermostatic switch 
is used to connect and disconnect it to the compressor as necessary. 
Expansion Valve 
The expansion valve determines the correct amount of refrigerant going into the 
evaporator, and it lowers the pressure of the refrigerant. 
When the compressor starts, the expansion valve opens and the liquid refrigerant 
flows through a strainer in the high pressure liquid inlet. Once in the expansion 
valve, the refrigerant is correctly pressurized. As the evaporator calls for more 
refrigerant, the expansion valve allows the required amount of low pressure liquid 
refrigerant into the coils. 
The expansion valve maintains the delicate balance between the heat load and the 
cooling efficiency of the evaporator. 
Discharge/Suction Service Valves 
Discharge and suction service valves allow the air conditioning system to be emptied 
and filled. These valves also provide places where the system can be checked with 
pressure gauges
Note: Some systems use a Schrader valve in place of the discharge and suction 
valves. This is a spring-loaded valve which looks rather like the valve in a tire. 
The Compressor Relay 
A capillary tube from a cycling switch lets the switch know what the temperature is in 
the evaporator. This switch turns the compressor on and off to keep the evaporator 
temperature at about 32 to 45 degrees F. The relay switch keeps moisture from 
freezing on the evaporator core. 
Electric Air Conditioning Fan 
Sometimes an extra electric fan is placed in front of the condenser to provide an 
extra flow of air during warm weather, or for times when the car has to idle for a 
long time. You activate and deactivate the air conditioning fan when you turn it on 
and off at the control panel. 
Compressor Belt 
The compressor is engine driven by a belt on the front of the crankshaft.
                   Car Air Conditioning removes the "HEAT" from inside the car cabin.
   Classic Cars Air Conditioning Specialists.

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